This invention pertains to the art of sensing devices and more particularly to sensing devices for sensing individual articles passing along a work path.
The invention is particularly applicable to a sensing device for sensing individual newspapers, magazines and the like passing in a continuous stream along a processing line in an overlapped relationship relative to each other and will be described with particular reference thereto. However, it will be readily appreciated by those skilled in the art that the invention has far broader applications and may be advantageously employed in many other environments for sensing articles wherein there is relative movement between the sensing device and the articles themselves.
Printing presses, bindery equipment and the like most commonly deliver newspapers, magazines and other printed articles in a continuous stream with one of the edges of each article overlapping a portion of the next adjacent article. Typically, in this overlapped condition, the leading edges of adjacent articles are pitched or spaced apart from each other. Depending on the size and type of article involved, this spacing may vary from as much as several inches to as little as less than one inch. In these continuous streams of articles, the articles are not always precisely located or lapped relative to each other such that there are many misaligned articles and variations in the spacing between consecutive articles.
Sensing units are utilized to detect the individual articles as they pass along the continuous stream in order to count the articles and control attendant stacking, bundling and binding machinery. Heretofore, the misaligned articles have made prior sensing devices unreliable when combined with high speeds at which modern printing lines operate. Modern newspaper printing presses can deliver over 20 papers per second and it is common, for example, to deliver 20 papers per second at an average of 3 inches apart. This requires a stream velocity of 60 inches per second or 300 feet per minute. When individual articles are misplaced to be 1 inch apart in a stream moving at 60 inches per second, the resultant instantaneous rate presented to a sensor is 60 articles per second. Thus, it is necessary to provide for quick acting and accurate sensing means in order to maintain an accurate count of the articles flowing along the stream.
Misplacing and misalignment of articles in the stream is quite frequent. Such misplacing and misalignment are not only caused by the attendant preceeding machinery, but are also caused by persons along the line removing one or more of the articles for inspection or the like and then reinserting them into the stream. Uneven spacing between the articles causes variations in stream thickness since more closely spaced lapped articles results in more articles being overlapped in that section. In addition to variations caused by spacing, the thickness varies with that of the individual articles themselves. For example, the number of pages in a newspaper varies from day to day and will, therefore, affect the average stream thickness or height. The leading surface or edge of newspapers being delivered along the stream is usually the folded edge and the folds may be tight or relatively loose and bulbuous. Sections within a newspaper may be improperly collated and may also contain wrinkles, holes and other defects. All of the above specifically mentioned anomalies render it difficult to sense and count newspapers, magazines and other articles accurately.
Elimination of problems caused by inaccurate sensing of such articles has been the focus of some substantial attention by both publishing groups and engineers. Far more papers and magazines are printed than can normally be accounted for and some packages of papers or magazines contain too many or too few articles. Moreover, stackers and other attendant article handling equipment are caused to malfunction. The combination of variables existing in a stream of papers has resulted in many prior efforts to perfect a sensing device and method which would accommodate the specific variables discussed above and accurately sense individual articles. These prior efforts have culminated in many different types and styles of sensing devices and methods which have met with varying degrees of success. Some printing lines employ more than one type of sensing device depending on the specifics of the stream conditions and/or technical adjustments are made on the sensing devices on a day to day basis depending on the nature of those articles which will comprise the stream itself. The lack of an accurate and reliable article count has come to be simply tolerated rather than accepted since no sensing device and method has yet been developed to overcome all the above problems encountered in such processing lines.
Substantially all of the sensing devices and methods presently in use in the preferred environment for the subject invention depend on physical contact with the articles in the stream. For example, some prior devices have utilized sensing wheels which are placed in contact with the article stream for rotation thereby. The sensing wheels, in turn, cause periodic activation of a transducer as they are rotated in order to maintain a running count of the individual stream articles. However, these prior constructions have had several drawbacks from structural and operational points of view. First, many have been rather complicated in design and, therefore, subject to maintenance problems. The sensing wheels of these prior devices have been such that they were inherently subject to yielding "false" readings or counts due to variations in the stream configuration. To counteract the potential for such "false" readings or counts, it has been necessary to place a biasing force either on or adjacent the sensing wheels to prevent counter rotation thereof. This biasing means made it more difficult and required more force to rotate the sensing wheels in the desired direction to achieve a stream count. Thus, these prior devices require a sensing wheel indexing force which is higher than that which can be provided by small or light papers flowing along an article stream. Still further, the basic geometric configurations of prior sensing wheels have not taken optimum design criteria into full consideration.
All prior efforts to develop non-contacting types have proved unsuccessful and provided unacceptable results. Photo, ultrasonic, fluidic and laser are some of the energy forms utilized in prior attempts at non-contact sensing. Failure of these non-contacting devices and methods has been due to variables in color, conformation, shape, positioning, spacing and the like which are all intrinsic in a stream of newspapers, magazines and like articles.
The present invention contemplates a new and improved method and apparatus which overcome all of the above referred to problems and others and provides a new sensing device and method which are simple, economical, accurate, operable at a high rate of stream speed and which are readily adaptable for use in sensing a wide variety of articles moving along a work path in many other environments.